1. Field of the Invention
This invention relates to a robot system for carrying out a desired operation through control of a hand mounted on a wrist at an end of a robot arm thereof, and more particularly to a robot system of this kind having a robot mechanical unit and a robot controller integrally combined with each other.
2. Description of the Related Art
A conventional robot system comprises a robot mechanical unit including a robot arm and a robot controller which are provided as separate units and electrically connected to each other by a connector cable. Operation commands are given from the robot controller to direct the robot mechanical unit to carry out desired operations.
According to one conventional method of establishing the connection between the robot mechanical unit and the robot controller, the robot controller is installed at a location remote from the robot mechanical unit, and then a long connector cable is laid to connect the robot mechanical unit and the robot controller to each other. This method of connection between the robot mechanical unit and the robot controller, however, requires an additional space for installation of the robot controller, as well as a facility for protecting the connector cable. Therefore, provision of the robot mechanical unit and the robot controller at locations remote from each other by utilizing the long connector cable is not suitable for efficient utilization of a limited space and facility available for the robot system.
One solution to these inconveniences is to directly connect the robot mechanical unit and the robot controller to each other by respective connectors thereof. In doing this, the robot controller is installed adjacent to the robot mechanical unit in a dead space outside of the operation range of the robot arm.
FIG. 3 shows the construction of a conventional robot system of this kind. In FIG. 3, reference numeral 20a designates a robot controller received within a housing and installed adjacent to a robot mechanical unit 10a. A connector 30 provided on the robot controller 20a and a connector 31 provided on the back of a base 11a of the robot mechanical unit 10a are coupled to each other, thereby establishing the electrical connection between the robot controller 20a and the robot mechanical unit 10a.
The robot mechanical unit 10a including a robot arm is fixed to the floor by the base 11a thereof. Arranged on top of the base 11a is a swing device 18a with rotational axes J1 and J2, which has one end of a J2 arm 12a connected, thereto. Further, one end of a J3 arm 13a is connected to the other end of the J2 arm 12a via a swing device 19a having a rotational axis J3. A wrist 14a is provided at the other end of the J3 am 13a, and various kinds of hands can be mounted on the wrist 14a. The center of the wrist 14a is called the TCP (Tool Center Point). The operation range of the robot arm means a range of operation within which the TCP can be moved.
By reducing the size of the robot controller 20a such that it can be installed in a dead space outside the operation range of the robot arm, it is possible to arrange the robot controller 20a adjacent to the robot mechanical unit 10a. The applicant has already proposed a robot system of this kind by Japanese Patent Application No. 5-259635.
Generally, a robot controller contains a part generating much heat, such as a servoamplifier. To cool the interior of the robot controller, the controller is required to have a large radiating surface as a whole, or alternatively, it is necessary to carry out forced cooling by the use of a cooling fan or the like.
The robot controller installed adjacent to the robot mechanical unit is reduced in size as described above, and hence cannot secure a sufficiently large radiating surface. Further, a large cooling fan cannot be provided for forced air-cooling of such a robot controller reduced in size. Even if a small cooling fan is provided, it cannot achieve sufficient cooling effects, since a passage is also narrow through which air should be circulated by the operation of the cooling fan.
Thus, the robot controller of the type provided integrally with the robot mechanical unit has the inconvenience that it is difficult to cool the inside thereof due to the reduced size thereof.
Further, in spite of the fact that it is desired that the robot controller is reduced in size as much as possible to be installed in a limited space, it is difficult to reduce the size of the robot controller beyond a certain level since it contains a servoamplifier which generates much heat and has a large volume.